ABSTRACT The presence of hypoxia in a many human tumors is a widely observed negative prognostic indicator. Laboratory experiments in animal models and in vitro systems are consistent with the clinical observations showing that hypoxia is a major driving force in cancer progression. Since hypoxia is difficult to control and measure in animal models, in vitro approaches offer the best opportunity for detailed molecular analysis of the influence of oxygen on cancer initiation, progression and analysis. However, clinical tumors display a range of oxygen levels with some regions that are chronically hypoxic whereas other regions experience time- dependent changes, i.e. cycling hypoxia. This further complicates systematic analysis of hypoxic responses as there are literally an infinite number of static and cycling hypoxia patterns that can be probed. To date, studies of cycling hypoxia usually are limited to probing a single, arbitrarily chosen cycling pattern that may not be clinically relevant. In order to facilitate screening of both chronic and dynamic changes in hypoxia, we propose to develop a technology that can deliver a range of hypoxia levels, either static or cycling, to each row of a standard multiwell tissue culture plate. This allows monitoring of molecular adaptation, cell growth and drug response under a range of oxygen concentrations simultaneously. The initial studies will demonstrate the technology on a standard 96-well plate format that is compatible with current multichannel pipettors, plate readers and laboratory protocols that allows immediate adoption to any oncology laboratory. The same principles can be used in any multiwell plate to aid in assessing the effect of oxygen on cell growth and viability, tumor progression, biomarker identification and therapy response. There is no current technology that allows these types of investigations in a standard high-throughput format. This technology addresses at least two areas of interest in the RFA as it will aid in (i) the elucidation of the basic mechanisms underlying cancer initiation and progression and (ii) facilitate/accelerate the processes of drug discovery.